hcThe question is specific to tapped flanges and tapped pipe caps. I should clarify that. I’m not speaking to tapping pipe in any way.
My experience has always been to use a half couplings on tapped flanges and pipe caps and this included 150# thru 900# connections. I was taken a back by my piping manager when he said it was too fancy a connection. I think JOP surprised me now as well.
Like 11echo says you simply cut a hole in the pipe cap or flange, insert the coupling and back weld. At Imperial oil it was typical practice to tap ALL blinded flanged connections with a 1 inch bleeder valve as a back check to verify positive isolation before making a tie-in in the future. Using a half-coupling was standard practice.
To use a 1″ Olet on a pipe cap for example my thought is you would need to grind out the curve in the Olet to it being relatively flat because its curved in one direction to go on a pipe. Then you would need to fill it the curve of the pipe cap against the Olet which could be alot of welding depending on size. Correct me if I’m wrong.
The flatolet on a blind flange would work fine but, I would think it would be slightly more costly because the back weld on the olet would be larger than the coupling. Plus the olet is quite a large fitting on the blind compared to the half coupling. Not really a selling feature there but, it makes sense to me that using a half-coupling for these applications just makes sense.